This invention relates to an independent wheel suspension for a wheel of a vehicle. More specifically, this invention relates to a wheel suspension for the steerable wheels of an automotive vehicle, of the type which comprises a wheel carrier having a steering linkage lever, upper and lower control arms connected to the wheel carrier, and a steering tie rod connected on one end to the steering linkage lever, and on the other end to a steering mechanism, such as a reversing gear train operable by a rack and pinion steering unit.
An independent wheel suspension having these features is described in German Patent No. 1,286,413. In the wheel suspension described there, the steering linkage lever is located approximately at the level of the steering knuckle pin of the wheel carrier. Thus, this component is located in the space between the wheel and the vehicle body, which also includes the steering tie rod articulated to the steering linkage lever.
This arrangement of the steering linkage lever leads to strong intrinsic steering forces on the wheel when the wheel is subjected to large vertical movements such as might be caused by driving over rough terrain. In addition, the arrangement of the steering linkage lever on the inside of the wheel requires a large amount of space. Such wheel suspensions are therefore unsuitable for cross-country vehicles which have a trough-like body structure filling the space between the wheel suspensions, and in which it is desirable to maximize the useful inner body space with respect to the total width of the vehicle.
Therefore, an object of this invention is to provide an independent wheel suspension, of the type described above, which is suited for use in cross-country vehicles, and particularly in special-purpose vehicles having a trough-like body structure in the area between the wheel suspensions. Another object of this invention is to provide a space-efficient suspension which allows for large vertical movement of the wheel, without the resulting disadvantageous development of intrinsic steering forces on the wheel and steering mechanisms. An additional object is to provide a wheel suspension which is well suited for ensuring a favorable action on the elements of the wheel suspension under very high loads, such as those which might occur in a cross-country vehicle.
These and other objects are attained in a wheel suspension which comprises a wheel carrier having a steering linkage lever formed at its upper end, a lower control arm connected to the wheel carrier, a generally horizontal steering tie rod which extends in a direction which is generally parallel to a longitudinal axis of the vehicle and which is connected at one end to the steering linkage lever and at a second end to a steering mechanism, and an upper control arm which is generally horizontal and extends in side-by-side relation with the steering tie rod and which has an effective length approximately equal to that of the steering tie rod. The upper control arm is connected at one end by an upper control joint to the wheel carrier at a point which is located laterally of and above the wheel on the body side of the wheel, and is pivotably connected on a second end to a bearing member, such that the control arm is pivotable about a bearing axis which extends obliquely from an imaginary point of intersection with a central transverse vertical plane which bisects the wheel. Additionally, the bearing axis of the upper control arm bearing member extends from the outside toward the inside of the vehicle and toward a vertical longitudinal center plane of the vehicle in a direction which is rearward, with respect to the front of the vehicle, and which is upward with respect to the center plane. The steering linkage lever extends transversely from the wheel carrier to a point of connection with the steering tie rod which is located over the apex of the wheel. The lower control arm is connected to the wheel carrier and to the vehicle body so as to form a transverse control arm having a lower bearing axis which is essentially parallel to a vertical longitudinal center plane of the vehicle and which is substantially horizontal. Alternatively, the lower bearing axis may be slightly inclined from the horizontal. The steering mechanism comprises a reversing gear train which has a lever arm connected to the steering tie rod at a point which is located over an apex of the wheel.
The arrangement of the steering linkage lever in accordance with this invention makes it possible to locate the steering tie rod above the wheel. Accordingly, no space need be provided for accomodating the steering linkage lever and the steering tie rod between the vehicle body and the wheel.
Furthermore, the lower control arm, extending perpendicularly away from the vehicle body, can be relatively short in design so that relatively little space is required for its accommodation.
It is thus possible to reduce the spacing between the wheel and the vehicle body, especially in the upper zone of the wheel periphery, and/or to correspondingly broaden the size of the vehicle body structure to gain useful interior space for the vehicle. This advantage is especially significant in special vehicle types having trough-like bodies which extend between the wheels relatively far in the downward direction and which widen toward the top in the lateral direction.
The essentially unidirectional arrangement of the steering tie rod and the upper control arm, and their approximately equal effective lengths, ensure that the wheel will not be subjected to wheel suspension induced steering forces during any wheel movements taking place during jouncing and rebounding.
In a particularly advantageous embodiment of the invention, the arrangement of the upper and lower bearing axes, as described above, make it possible to coordinate the kinematics of the wheel suspension in such a way that during jouncing and rebounding any changes in camber, as well as toe, of the wheel are avoided in spite of the large vertical wheel motions.
Furthermore, it is ensured that forces acting on the front section of the wheel (i.e., the part of the wheel adjacent to the steering tie rod, as viewed in FIG. 4), subject the steering tie rod to tensile, and not compressive stresses. Thus, an advantageous design of its cross section is made possible.
Furthermore, the connection points (or points of articulation) of the steering tie rod and the upper control arm can be positioned such that the components of the steering unit required for operating the steering tie rod can be mounted in the vehicle at a location where they occupy space not required for other installations and accessories. This is important, particularly in special-purpose vehicles wherein the position of the vehicle operator is to be in maximally close proximity to the front of the vehicle. In these vehicles, the space that would otherwise be occupied by the steering unit is needed for the pedal array located in the floor area directly in front of the operator at the forward end of the vehicle.
The wheel suspension of this invention is also suitable for vehicle wheels that are not steered. In this case, the steering tie rod is articulated (i.e. connected) to a joint attached to the body and, thus, takes over the function of a longitudinal strut for wheel guidance. With the aid of this tie rod, the wheel carrier can be blocked in a neutral position or with a desired toe angle. Accordingly, the steerable wheels, as well as the wheels of a vehicle that are not steerable, can be supported by means of essentially identically constructed wheel suspensions.
As noted, provision of the steering linkage lever on the upper portion of the wheel carrier makes it possible to install the reversing gear train, which operates the steering tie rod, in a relatively high level position with respect to the wheel axle. It is therefore possible to accommodate part of the steering mechanism in the front portion of the vehicle at a relatively high level. This part of the steering mechanism is located above the pedal array in a zone relatively remote from the operator. Thus, practically no useful space is occupied by this mechanism.
The reversing gear train of the steering mechanism is located within a protective cap. This arrangement ensures optimal protection for the gear train. The protective cap can simultaneously be utilized as the bearing bracket for the upper control arm bearing member.
A wheel suspension according to this invention can be designed so that two or more wheels on the same side of the vehicle are steerable by means of the steering linkage associated with the foremost wheel suspension. The resulting double-armed design of the steering lever offers an advantage in that the steering transmission rod leading respectively to the subsequent wheel suspension can be located within the vehicle body. This is important, particularly for vehicles with a smooth outer contour. However, it is also possible to locate the steering transmission rod above the upper control arm of the wheel carrier, preferably above the wheels and beside the vehicle body.
A wheel suspension wherein the upper control arm and the steering tie rod extend toward the rear of the vehicle is also within the scope of this invention. In this case, the same advantage can be attained with respect to the arrangement of the wheel steering system. The difference is that the elements of the steering mechanism accomodated within the vehicle body are located in a zone which is relatively far removed from the front end of the vehicle. This can prove to be advantageous in cross-country vehicles having a front-located engine.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.